Experimental Study On The Effect Of Filling Medium Characteristics On Stress Wave Propagation In Jointed Rock Mass

The propagation law of explosion stress wave in jointed rock mass is closely related to the characteristics of joint filling medium,which is shown in that the water content and thickness of filling medium affect the absorption capacity of explosion stress wave.Taking the layered jointed rock mass in Guizhou Province as the background,it is found that during the construction of horizontal jointed tunnel,due to the erosion of water and the weathering and metamorphism of rock mass,the argillaceous interlayer in the joints will cause the leakage of explosion energy and the premature escape of explosion gas,which seriously hinders the propagation of explosion stress wave,resulting in underexcavation of tunnel contour,too large blasting debris,and the failure of blasting,the utilization ratio of blast hole is greatly reduced,it directly affects the blasting effect.Therefore,based on the stress wave propagation theory and typical engineering conditions,the red clay exposed in the project site is used as the filling medium,the mortar red clay mortar composite specimens with different water contents(36%,39%,42%,45%)and thickness(3mm,6mm,9mm)were designed,dynamic compression tests of different impact pressures(0.3MPa,0.4MPa,0.5MPa,0.6MPa)were carried out with a 50 mm diameter variable cross-section split Hopkinson pressure bar.The effects of joint medium characteristics and strain rate on stress wave propagation,dynamic compressive strength,dynamic stress-strain relationship,energy dissipation law and fracture characteristics of jointed rock mass are studied from the aspects of stress wave strength,energy and failure characteristics.The main research contents and achievements are as follows:(1)With the increase of the thickness and water content of the filling medium,the effective stress of the composite specimen decreases gradually,the delay time of the stress wave propagation increases,and the barrier effect of the joint on the stress wave increases significantly;With the increase of the loading pressure,the effective stress of the specimen increases gradually,and the time to reach the peak stress decreases gradually.(2)With the increase of the thickness and moisture content of the filling medium,the dynamic compressive strength and dynamic elastic modulus of the composite specimen decrease gradually,while the dynamic peak strain and post peak deformation of the specimen increase,indicating that the increase of the thickness and moisture content of the filling medium improves the plastic deformation energy of the specimen.(3)Dynamic compressive strength and peak strain have obvious strain rate effect,but with the increase of filling medium thickness and water content,their sensitivity to strain rate gradually decreases.(4)With the increase of filling medium thickness and water content,the reflected energy density increases,while the transmission energy density and dissipation energy density decrease.The incident energy EI,reflected energy ER,transmitted energy ET and dissipated energy ED are positively correlated with the strain rate.With the increase of strain rate,EI,er,et and ED increase continuously,and the energy growth rate is EI>ER>ET>ED.(5)The existence of joints greatly weakens the destructive effect of stress wave on rock mass,and the weakening effect becomes more significant with the increase of filling medium thickness and water content.The change of joint medium characteristics(thickness and moisture content)leads to the great difference of mortar damage degree,fragment size and quantity on both sides of joint.Figure[50]table[9]reference[69]...